Re: SGA Sizing problem

Parris Geiser (parris_at_walleye.esp.bellcore.com) wrote:
: Thomas,
: Thanks for your reply.
: Yes the scripts that you provide do give what ORACLE thinks
: is the size of the SGA. What I'm confused about is that the
: UNIX ipcs -b -m command value is such a different number.
: Perhaps ipcs is not giving what I thought or ...???
: Parris

: Thomas J Kyte (tkyte_at_us.oracle.com) wrote:
: > parris_at_walleye.esp.bellcore.com (Parris Geiser) wrote:
 

: > >Running 7.1.6 on HP-UX.
 

: > >db_block_buffers = 100
: > >shared_pool = 3,500,000
: > >log_buffer = 16,384
: > >block_size = 2048.
 

: > >So, the SGA should be: 3,721,184.
: > >But when I do an ipcs -b -m
: > >I get 4,892,680.
 

: > >The question is: why such a large descrepency?????
: > > Thanks.
 

: > Run the following two queries in your database, they will show you exactly how
: > the sga is being allocated and what it is being used for.

: > compute sum of Value on report
: > break on report
: > column value format 999,999,999
: > select * from v$sga;

: > column bytes format 999,999,999
: > compute sum of bytes on report
: > select *
: > from v$sgastat;

: > The variables you listed have by far the largest effect on the SGA size but they
: > are not the only things up there.
 

: > Hope this helps...
 

: > Thomas Kyte
: > tkyte_at_us.oracle.com
: > Oracle Government

Don't forget, the memory you see used when you issue the 'ipcs' command include the block buffer cache (multiply the number of db_block_buffer by the db_block_size). This will get you closer to the 4.5 M !

There are, of course a number of other cache's, buffers, message queue areas, whatsidoodles and thing-a-me-bobs that are allocated in there as well. (log_buffer_size, sort_area_size off the top of my head).

Michael Marsden

-- 
Michael Marsden                   "It's the car, right ? Chicks dig the car"
ORACLE Database Consultant                              -- BATMAN Forever --
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Disclaimer: I own the company so I can say what I like !